Overmolding is a process where a melt processible material is molded directly into a rigid component, known as an insert or substrate. Melt processible materials typically used in overmolding include elastomers and thermoplastics. The major overmolding processes includes insert molding and two-shot molding. Materials are usually chosen specifically to bond together, using the heat from the injection of the second material to form that bond that avoids the use of adhesives or assembly of the completed part, and results in a robust multi-material part with a high quality finish. Reinforcing Fiber prepreg materials are then in thermoplastic, that is then heated to above the thermoplastics meting point and then put in a steel mold to conform to a mold platen shape. Unfortunately, the cutting and lay-up work with such sheets are unfavorable in terms of production cost and throughput.
Insert overmolding also has met with limited acceptance in instances where there is a desire to adjust the insert properties owing to the finite grades of thermoplastic woven fibers available. While custom weaves to include fibers that vary in properties are readily produced, a custom process necessary increases lead time for production and has limited value in tuning properties as the variations available in fiber thickness and fiber count per unit area.
While non-woven thermoplastic fibers and even chopped, non-oriented thermoplastic fibers afford benefits in terms of material cost, any benefit is overshadowed by the reduced insert strength and does little to tune the insert property of density.
Thus, there exists a need for process for insert overmolding that overcomes the limitations associated with heat forming of woven thermoplastic fibers. There further exists a need to achieve insert thermal formation from non-oriented thermoplastic fibers to achieve a wide range of insert properties.